Digital X-ray has the potential to overcome limitations of screen-film systems, including higher detection efficiency, significantly wide dynamic range, contrast enhancement, and post processing capabilities such as computer-aided diagnosis and web base instantaneous access to the images by multiple expert radiologists. Furthermore, digital data acquisition enables the exploration of novel imaging techniques such as tomosynthesis, dual energy X-ray, and digital subtraction imaging. CT and PET scans are also well known X-ray techniques. Advancements in technology in the past decade have now made it feasible to obtain large area high-quality images using digital detectors. These utilize a scintillator as the primary detection layer to convert X-rays to light. This light is subsequently converted into an electronic signal by various photoelectric sensors such as charge-coupled devices (“CCDs”) and amorphous silicon photodiodes (a-Si:H). Results from clinical trials suggest that in static imaging, digital methods give results comparable to photographic film. In methods that rely on photon counting (such as computerized tomography (CT) or positron emission tomography (PET), film has no application. Both of these methods can benefit from the development of efficient, fast and economical converters of X-rays to electrical signals. One category of such converters is called scintillators, which convert X-ray photons to visible light photons, subsequently detected by photomultipliers or solid-state devices.
Scintillators are generally made from single crystals. Relevant examples are the two lutetium silicate compounds (ortho- and pyro-) mentioned above, to which cerium has been added as a dopant to provide the desired emission. Some materials, however, are not readily grown as single crystals, either because of their extremely high melting points or because they decompose before melting. Relevant examples are lutetium oxide and gadolinium oxysulfide (GOS), respectively. In such cases it is sometimes possible to prepare the scintillator from sintered powders. Conventional wisdom views such powder consolidation techniques as merely a last resort, and the product as less than adequate approximations to the ideal. According to this view, there is no reason to fabricate a scintillator as a ceramic when the material is already available as a single crystal. As will be seen, however, this invention contravenes conventional wisdom, and demonstrates that the lower fabrication temperatures can improve some of the scintillation properties of the ceramic to be actually superior to those of a single crystal of the same composition.